Thanks to Gutis, many spell method have been documented in this post: SPEL API methods
Note that either if the community will try to help you here you are on your own with spell as mentioned before this is not supported by CA. Wrong spell can dramatically hurt so must always been used as last solution.
Others customization are mostly javascript in your htmpl files or use of WSP and schema designer
Many function/method can be discover reading the files in the bopcfg folder. in the magic and interp folders for Spell and in the www\wwwroot\scripts for javascript
Hope this help
/J